Inductance-coil for telephone-lines.



S. B. KENT. INDUCTANCE COH. FOR TELEPHONE LINES. APPLICATION FILED SEPT.12.1914- 1,158,810. Patented Nov. 2. 1915.

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S. B. KENT. INDUCTANCE COIL FOR TELEPHONE LINES.

APPLICATION FILED SEPT. 12. 1914.

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INDUCTANCE 0011 FOR TELEPHONE LINES.

APPLICATION FILED SEPT-12,1914.

Patented Nov. 2, 1915.

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UNITED STATES PATENT OFFICE.

STANLEY B. KENT, OF NEW YORK, N. Y.. ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF NEW YORK, N. Y.. A CORPORATION OF ILLINOIS.

INDUCTANCE-COIL FOR TELEPHONE-LINES.

Specification of Letters Patent.

Patented Nov. 2, 1915.

Application filed September 12, 1914. Serial No. 861,393.

T 0 all "whom, it 771 (1y concern Be it known that I, STANLEY B. KENT, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Inductance- Coils for Telephone-Lines, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone lines, and its objects are to simplify the construction, to lessen the cost of manufacture, and

to increase the elficiency of inductance coils therefor and particularly of a certain type of loading coil having discontinuous cores.

It has been found of great advantage to construct the cores of loading coils with airgaps, thus providing demagnetizing poles which act to reduce the amountof residual magnetism in the iron core when the line windings have been subjected to lightning or other strong foreign currents. \Vithout such air-gaps, the inductances of the coil winding will vary from time to time, causing singing of the repeaters, or when the line is subjected to superposed telegraph currents the telephonic transmission qualities,of the line will be seri usly impaired. In fact, an enormous gaixi in telephonic transmission is possible by combining amplifying repeaters with loading coils having discontinuous or air-gap cores, and a substantial improvement is secured in the quality of telephonic transmission in the case of telegraph working on telephone lines loaded with such coils.

In a phantom telephone line system, the phantom circuit loading coil usually requires four sets of windings, one for eachof the four line conductors of the system, each line winding including the outer sectional winding on one quadrant of the core connected in series with the inner sectional winding on the oppositecore quadrant. It has been proposed to build such loading coils with cores divided into four sections by four air-gaps located between the winding sections, thus producing a discontinuous core wholly symmetrical with respect to the windings. Such symmetry was required on account of the necessity of balancing the admittances between the several core windings toavoid crosstalk between the different circuits of the system. Four air-gaps, however, are undesirable from a manufacturing standpoint as the cutting of so many gaps and the assembling of the parts after cutting, seriously increases the difficulties and the cost of manufacture, and reduces the efiiciency of the coil.

It is inrespect to phantom coils of this general type that the present invention is particularly applicable, and the matter of reducing the number of air-gaps without introducmg an unbalanced condition that would cause crosstalk, which is the'particular purpose of this invention, is met in accordance therewith by electrically connecting the separated core sections. Instead of four core sections, the coil may thus be constructed with only two sections separated preferably by diametrically opposite airgaps located between adjacent coil windings, a conductor being provided to join the sections electrically. This conductor is preferably a non-magnetic metal pin or a plurality of pins pointed at each end and piercing one or both of the core separators and the adjacent core sections.

The invention will be more fully understood by reference to the accompanying drawing, in which Figure 1 illustrates the core of a phantom circuit loading coil partly insulated; Fig. 2, the same fitted with winding heads and separators, and showing the inner windin on one section completed. Figs. 3 and 4, the same when wound; Fig. 5, a machine for cutting gaps in the core; Fig. ,a fragment of the coil in section showing one gap spacer and conducting pins piercing the core secpleted coil, the latter being partly in section.

' Referring first to Fig. 8: The core of a hantom loading coil is shown separated into two sections. 1" and by air-gaps 3 and 4. Eight winding sections 5 tom inclusive are indicated in the positions they occupy generally to the core sections. Eachof'the four line conductors 13 to 16 of the phantom system includes an outer sectional winding, say 5, on one core quadrant inseries with'an inner sectional "winding, 6, on the opposite core quadrant. T heliiie conductors 13 and li comprise one of the side circuits extending between telephone stations '17 18; conductors l5. andlfi constitute another side circuit extending between stations 19 and 20, and the four conductors together make up the third or phantom circuit extending between stations 21 and 22. The two core sections are electrically connected by one or more non-magneticconducting pins 23. If the conducting path through this pin from core section 1 to'core section 2were notpro vided, there would be a path for crosstalk between the side circuit 13, I l and the side circuit 15, 16 on account of thecapacity due to the close proximity of the inner windings 8, 11. and 6, 9 and the core sections 1 and 2, respectively, and thus an unbalanced condi tion resulting from the division of the core.

into a less number of sections than the winding sections. To explain this unbalance, let

"it be assumed that telephonic conversation is being carried on from station 17 to station 18, and that the pin 23 is not present, crosstalk would take place over the following circuit: From conductor 13, through outer winding 5 to inner winding 6, thence to the core section 2 and to the inner winding 11, thence through the repeating-coil windings 2d and 25 in parallel to conductor 15, thence by way of inner winding 9, core section 1 and inner winding 8, to the opposite conductor ii of the originating circuit. By electrically connecting the core sections 1 and 2, this by-path for. crosstalk is short-circuited so that the only effect is a slight and negligible shunting of the telephonic currents generated in either ofthe side circuits. The remaining figures of the drawing illustrate the construction of the preferred embodiment of a phantom loading coil according to the invention. In manufacturing thin steel guides 31 are placed over the core in the position occupied by the separators 2.9, and the gaps are cut by the band-saw 32 working between the guides. After the cutting operation the two sections of the coil are brought together against gap spacers 33, one at least of which has conducting pins 23 held therein. These pins pierce the adjacent core sections between the iron.wires thereof. The sections are held together with the gap spacers therebetweenby aclamp 34, which is preferably of metal having high electrical resistance characteristicsto avoid eddy cur rent losses from stray magnetic forces. The two parts of the clamp 3% are drawn together and about the coil by bolts 35. The ends 36 of the windings are brought to the outside of the coil as shown, and the coil'is bound with heavy cord 37 to protect the windings and insulation.

While the invention is especially applicable to phantom loading coils having a lesser number of air-gaps than corewinding sections, it is not intended to belimited to such. coils, inasmuch as the joining by electrical conductors of separated core sections may be found useful in other types ofloading coils and also in coils for other purposes.

VV hat is claimed is:

1. An inductance coil comprising a core formed in separated sections, and a conducsheets and joining said core sections electrically.

4. An inductance coil comprising a core formed in separated sections, non-conducting spacers between said sections, and a conducting pin extending through one of said spacers and electrically contacting with said core sections. v

5. An inductance coil comprising a core formed in separated sections, spacers of nonconducting sheet material between said sections, a plurality of conducting pins supported by at least one of said spacers and electrically contacting with said core sections.

6. An inductance COIl comprismg a core of magnetizable wire, said core being formed in separated sections, spacers between said sections, and a conducting pin pointed at each end piercing one of said spacers and the adjacent core sections. 7

i 7. In a phantom loading coil the combination with a core and line windings distribmy name this 11th day of September, A. D. uted on a plurality of sections thereof, the 1914. said core being formed in separated sections TAULFY B. KENT. less In number than the winding sectlons, s J

5 and means for balancing the adnuttances lVltnesses:

between the several .hne wlndlngs. ALICE HAZLEY,

,In Witness whereof, I hereunto subscribe NANSA E. TUTHILL. 

